Minimally invasive diagnostic medical procedures are used to assess the interior surfaces of an organ by inserting a tube into the body. The instruments utilized may have a rigid or flexible tube and provide an image for visual inspection and photography, but also enable taking biopsies and retrieval of foreign objects. Analysis of image data collected during the inspection and imaging of the interior of the body cavity is a critical component of proper diagnosis of disease and other related conditions.
Examples of imaging devices presently used to view portions of the body convert an optical image to an electric signal. Well known types of silicon-based imaging devices capable of converting an optical image into an electrical signal include, for example, a set of charge-coupled devices (CCD) or complementary metal-oxide-semiconductor (CMOS) sensors. Two important characteristics of silicon-based imaging devices, such as the CMOS devices, are high noise immunity and low static power consumption. Significant power is only drawn when the transistors in the device are switching between on and off states. Consequently, the devices do not produce as much waste heat as other forms of logic, for example transistor-transistor logic (TTL). Importantly, silicon-based solid state imaging devices, such as the CMOS device, can only effectively duplicating optical images resulting from incident or direct wavelengths of light ranging from approximately 400 nanometers to approximately 1000 nanometers.
Non silicon-based solid state imaging devices (e.g., solid stated imaging devices based on Indium Gallium Arsenide (InGaAs), Indium antimonide (InSb), Mercury Cadmium Telluride (HgCdTe) are capable of detecting wavelengths of light greater than 1000 nanometers. However, these types of imaging devices require external readout devices as additional circuit components that cannot be fabricated on the same substrate as the detectors. Some also require a cooling component for proper operation. For example, InSb devices can only effectively operate under cryogenic conditions (about 80 degrees K.). Additionally, the pixel size of the Indium Gallium Arsenide (InGaAs) device is an order of magnitude greater than CMOS devices. Accordingly, certain optical components used in the imaging system must be larger to compensate, thereby increasing the cost, size, and weight of the overall optical system.